The small northern extension running from Interstate 490 through Greece to the Lake Ontario State Parkway is technically not an interstate highway but is marked as NYS Route 390. Note the change in the shape and color of the route signs, and some minor changes due to arcane state and federal roadway funding rules.

In the future, south of the Thruway, it may be renumbered I-99, as an extension of the Pennsylvania interstate along the US Highway 15 corridor that is planned to enter New York State SouthWest of Corning.

History

I-390 was originally going to be called I-486, as a spur route from a proposed I-86 in the Southern Tier. However, NY Route 17 did not become I-86 until 1999, 28 years after I-390 opened.

I-390 was also originally intended to continue due North into downtown Rochester instead of veering West on the south side of Rochester. This would have taken it along the Clinton Avenue corridor right through Brighton, the heart of Swillburg and the South Wedge. Needless to say, the kibosh got put on that plan pretty quickly once houses started going down. Brighton's Persimmon Park was created on land originally acquired for the ill-fated Genesee Expressway. The extra wide bridge on South Clinton Avenue where it crosses the Erie Canal was originally intended to carry this highway.